Parts feeders used in the manufacturing industry are well known. Typically, such parts feeders comprise various types of hoppers, vibratory-type bowls or centrifugal-type bowls containing a bulk source of parts. These devices are used to separate and orient parts and properly present them to a subsequent process or assembly device. Such devices are typically capable of feeding one part type or a very small family of part types.
The use of a vision-based flexible parts feeders is a relatively new phenomenon in the manufacturing industry which is gaining credibility. With the use of such vision-based parts feeders, companies are able to make their manufacturing systems more flexible by designing feeders with the capability to feed a very wide variety of parts. Doing so allows for a more cost effective means to automate the production of smaller volume products. Typically, in operation, such parts feeders deliver bulk parts from a source to a transport surface for inspection and subsequent picking therefrom by a robot. Preferably, a single camera is used to inspect the separated parts on the transport surface. The inspection is primarily used to identify which parts may be successfully grasped by a robot as well as the location of each identified "pickable" part. Flexible parts feeders also typically include a system for recirculating parts which cannot be grasped by the robot.
The performance and maximum feed rate of a flexible parts feeder is closely related to the feed rate, distribution, separation, stability and orientation of parts passing into the camera field of view as well as the performance of the vision system used therewith. Controlling these part attributes results in the ability to maximize the number of parts that can be inspected and successfully grasped by a robot in a given amount of time. The part feed rate into the camera field of view is preferably very consistent and controlled by the device which introduces parts from the bulk source. The distribution and separation of parts being inspected is preferably controlled by the conveyance portion of the feeder preceding the camera field of view. In addition, this conveyance portion also typically dictates the distribution, separation and, to some extent, the orientation (or number of stable states) of parts passing into the field of view which all affect the number of pickable parts during a given amount of time. The stability of parts as they pass into the camera field of view is also determined by the same conveyance portion and the means by which parts are transferred from the conveyance portion to the said transfer surface. It should be understood that if parts are bouncing around or not resting in the most stable orientations, additional part settle time is needed before inspection may occur which reduces feeder throughput.
One flexible parts feeder known in the prior art includes a series of tiered belts and an elevating bucket device for circulation of parts within the feeder. This parts handling technique results in a flow of parts through the feeder which is inconsistent due to a non-uniform part feed rate into the camera's field of view. In addition, parts are dropped from one belt to another in a way that results in a less than desirable part separation and additional undesirable part resting states. The belt which serves as the inspection surface is typically indexed back and forth to better spread out parts or is rapidly indexed to present more parts to the inspection camera. As a result additional parts settling time is required prior to inspection which limits performance and overall feeder throughput.
Another type of flexible parts feeder which is known in the prior art incorporates two pile-covered vibratory conveyor devices. In this type of parts feeder, a quantity of bulk parts is circulated on two opposing and side-by-side vibratory conveyors to move bulk parts in a generally circulating pattern. The conveyor vibrations and pile material are used to both convey and distribute parts into the field of view of a downward-looking camera which is located directly over one portion of one of the conveyor surfaces. The robot grasps parts directly off of the vibratory conveyor surface. This requires that the part must settle out prior to part inspection and grasping thereby decreasing feeder performance. Further, due to the nature of the bristle geometry of the pile material used for the vibratory conveyor, very small parts or parts with sharp protrusions tend to lodge in the pile material. As a result of the method employed to recirculate parts, control of part feed rate and part distribution through the feeder, and parts "sticking" in the pile material, feeder through put is limited (average feed rates in the range of 15 to 40 parts per minute).
Still another flexible parts feeder available on the market today includes a vibratory hopper for introducing parts from a bulk source, a relatively violent shake platen, a set of adjustable "fences" or gates for partially orienting parts and urging parts into a substantially single file prior to inspection and a belt which is indexed with rapid acceleration and deceleration to transport parts from the platen to the camera inspection area. Primarily due to the process of forming of the single file and the rapid indexing of the belt the rate of "pickable" parts presented to the camera field of view is limited to around 20 to 30 parts per minute.